I plan to buy a set and do a test this winter with my Performance Steering Wheel which shows peek speed of each lap.... I will do it on a road course...

I will

Run laps stock
Run laps with vent in hood taped off
Run laps with scoops
Run laps with scoops with vent in hood taped off

Do 4 laps each time.. And see if the peak speed at the end of the front straight changes... If they make a difference then a 140mph run with consistent start speed and start point will definitely tell the truth...

I plan to buy a set and do a test this winter with my Performance Steering Wheel which shows peek speed of each lap.... I will do it on a road course...

I will

Run laps stock
Run laps with vent in hood taped off
Run laps with scoops
Run laps with scoops with vent in hood taped off

Do 4 laps each time.. And see if the peak speed at the end of the front straight changes... If they make a difference then a 140mph run with consistent start speed and start point will definitely tell the truth...

I plan to buy a set and do a test this winter with my Performance Steering Wheel which shows peek speed of each lap.... I will do it on a road course...

I will

Run laps stock
Run laps with vent in hood taped off
Run laps with scoops
Run laps with scoops with vent in hood taped off

Do 4 laps each time.. And see if the peak speed at the end of the front straight changes... If they make a difference then a 140mph run with consistent start speed and start point will definitely tell the truth...

Thats cool but some simpler well controlled straight runs would be much simpler and more telling. Of course instrumentation is required.

My offer still stand to let somebody come to my house, borrow the Video VBox, and I'll point them to a perfectly lonely (straight) road near my house. Where's all the scoops fan-boys when you need them?

Does anyone know what the real purpose of the hood vent is? Is it just another point of air intake under throttle? Would sealing it create more of a ram air effect or would it just remove a legitimate point of cool air intake?

My offer still stand to let somebody come to my house, borrow the Video VBox, and I'll point them to a perfectly lonely (straight) road near my house. Where's all the scoops fan-boys when you need them?

Does anyone know what the real purpose of the hood vent is? Is it just another point of air intake under throttle? Would sealing it create more of a ram air effect or would it just remove a legitimate point of cool air intake?

They must have engineered it that way for a reason, no?

Yes, it was engineered for a reason. I don't recall the specifics, so, if more details are required, there's always . However, I have some general recollections: : a.) it's there for a good reason; b.) the engineers knew what they were doing; c.) sealing it would be a very bad idea.

Yes, it was engineered for a reason. I don't recall the specifics, so, if more details are required, there's always . However, I have some general recollections: : a.) it's there for a good reason; b.) the engineers knew what they were doing; c.) sealing it would be a very bad idea.

Yes, it's ludicrous to think the BMW engineers spent the effort and cost to install an intake that reduces performance. I'm not sure how someone could even think that.

Does anyone know what the real purpose of the hood vent is? Is it just another point of air intake under throttle? Would sealing it create more of a ram air effect or would it just remove a legitimate point of cool air intake?

They must have engineered it that way for a reason, no?

Thanks

I initially thought it was in an area of low pressure, however, it is most likely that it is in an area of high pressure which benefits the volumetric efficiency at large throttle openings.

I don't think the hood vent is a high pressure area, at least relative to the air box. At highway speeds after washing or in the rain I see water droplets blowing up/out of that vent. I think the main purpose is to keep cool air flowing through the air box even when you are at partial or zero throttle so when you first go WOT, the engine isn't getting a slug of hot air.

It probably helps at high RPM... The shorter the length for the intake the easier it is for the engine to get air at high RPM... This is just a guess to the hood vent. To imagine a situation think about when you're breathing really fast, for example right after a run around the block. Is it easier to breathe through a long piece of hose or a really short one? I bet the hood vent works in a similar fashion, there's much less duct work for air to flow through before getting to the engine making it much easier for the engine to breathe.

It probably helps at high RPM... The shorter the length for the intake the easier it is for the engine to get air at high RPM... This is just a guess to the hood vent. To imagine a situation think about when you're breathing really fast, for example right after a run around the block. Is it easier to breathe through a long piece of hose or a really short one? I bet the hood vent works in a similar fashion, there's much less duct work for air to flow through before getting to the engine making it much easier for the engine to breathe.

Although there could be some tract length effects my suspicion is quite a bit simpler. At higher rpm there is obviously a higher flow rate required and the total inlet area must support that flow with as little restriction as possible. Without the vent the front facing intake would probably choke the flow rate down too low. So using your analogy it is probably more like one big straw might make breating uncomfortable after a job, however, adding on additional small straw could be just enough to remove the discomfort.